The invention relates to a compound internal combustion and external combustion engine, and more particularly to a compound engine having working cylinders operated as a conventional internal combustion engine, preferably of the diesel-cycle type, co-operating with power cylinders of the external combustion type utilizing the normally wasted heat of the exhaust gases of the internal combustion working cylinders.
It is known that the efficiency of internal combustion engines is somewhat poor, and that a great portion of the wasted energy appears in the form of heat which must be dissipated by means of sometimes complex, and always energy-wasteful, air or liquid fluid cooling systems. A great proportion of the energy wasted in the form of heat is in the exhaust gases.
Diverse systems have been proposed in the past to recuperate, at least in part, the heat energy wasted in the exhaust systems of internal combustion engines, such as, for example, utilizing the flow of hot exhaust gases for driving a compressor or supercharger compressing the ambient air introduced into the air induction system of the engine, thus increasing the over-all efficiency of the engine.
Other arrangements have been used in the past for utilizing directly or indirectly the heat lost in the exhaust of an internal combustion engine and for converting the heat to useful mechanical energy which is returned as driving power to the engine. For example, U.S. Pat. No. 951,171 contemplates an internal combustion engine driving an air compressor and utilizing the heat from the cooling system coolant and from the exhaust gases, through the coolant, to heat the air between the compressor and the inlet of a hot air cylinder to which the compressed air is supplied. U.S. Pat. No. 2,826,894 discloses vaporizing the coolant of an internal combustion engine and running an auxiliary cylinder, coupled to the internal combustion engine crankshaft, as a steam engine. U.S. Pat. No. 3,877,229 discloses operating an internal combustion engine in a fuel-rich mode, afterburning the fuel-rich exhaust gases and utilizing the heat from the exhaust gases to heat and expand air supplied to a hot air engine coupled to the crankshaft of the internal combustion engine. U.S. Pat. No. 4,086,771 contemplates utilizing a gas cooling medium, rather than a liquid, in the coolant jacket of an internal combustion engine, and supplying the heated gas to working cylinders in which the heated gas is expanded prior to returning to the cooling jacket.